A bstract We compute the surface defect contribution to Rényi entropy and supersymmetric Rényi entropy in six dimensions. We first compute the surface defect contribution to Rényi entropy for free fields, which verifies a previous formula about entanglement entropy with surface defect. Using conformal map to
Sβ1×Hd−1 S β 1 × H d − 1 we develop a heat kernel approach to compute the defect contribution to Rényi entropy, which is applicable for p -dimensional defect in general d -dimensional free fields. Using the same geometry
Sβ1×H5 S β 1 × H 5 with an additional background field, one can construct the supersymmetric refinement of the ordinary Rényi entropy for six-dimensional (2, 0) theories. We find that the surface defect contribution to supersymmetric Rényi entropy has a simple scaling as polynomial of Rényi index in the large N limit. We also discuss how to connect the free field results and large N results.
Rényi entropies Sq are useful measures of quantum entanglement; they can be calculated from traces of the reduced density matrix raised to power q, with q ≥ 0. For (d + 1)-dimensional conformal field theories, the Rényi entropies across Sd−1 may be extracted from the thermal partition functions of these theories on either (d+1)-dimensional de Sitter space or R×Hd, where Hd is the d-dimensional hyperbolic space. These thermal partition functions can in turn be expressed as path integrals on branched coverings of the (d+ 1)-dimensional sphere and S1 × Hd, respectively. We calculate the Rényi entropies of free massless scalars and fermions in d = 2, and show how using zeta-function regularization one finds agreement between the calculations on the branched coverings of S3 and on S1 × H2. Analogous calculations for massive free fields provide monotonic interpolating functions between the Rényi entropies at the Gaussian and the trivial fixed points. Finally, we discuss similar Rényi entropy calculations in d> 2.
Entanglement entropy in even-dimensional conformal field theories (CFTs) contains well-known universal terms arising from the conformal anomaly. R\'enyi entropies are natural generalizations of the entanglement entropy that are much less understood. Above two spacetime dimensions, the universal terms in the R\'enyi entropies are unknown for general entangling geometries. We conjecture a new structure in the dependence of the four-dimensional R\'enyi entropies on the intrinsic and extrinsic geometry of the entangling surface. We provide evidence for this conjecture by direct numerical computations in the free scalar and fermion field theories. The computation involves relating the four-dimensional free massless R\'enyi entropies across cylindrical entangling surfaces to corresponding three-dimensional massive R\'enyi entropies across circular entangling surfaces. Our numerical technique also allows us to directly probe other interesting aspects of three-dimensional R\'enyi entropy, including the massless renormalized R\'enyi entropy and calculable contributions to the perimeter law.